This invention relates to methods of communicating via encrypted messages from one station to another on a communication network, and to circuits for implementing such communication methods.
Basically, a communication network of the type with which this invention is concerned includes at least one station which accepts messages from an operator, and which encrypts and transmits those messages; and it includes at least another station which receives the encrypted messages, decrypts them, and provides the decrypted message to an operator. Such networks are useful wherever proprietary information needs to be transmitted. For example, the proprietary information might include a recommendation from a broker to a client to purchase or sell certain stock, an electronic transfer of funds, military-related data, etc.
Typically, each person at the receiving station who is to receive a message has his own unique key, and the operator at the transmitting station has all such keys. Then, to encrypt a message for a particular person, the transmitting station uses the key which is assigned to that person.
In other words, in order to communicate between stations, certain individuals at both the transmitting station and the receiving station must "know" what the encryption/decryption key is. No one else can have access to the key, for if they do, they can monitor the encrypted message on the network and decrypt it. This, however, presents the problem of how to secretively transport the keys between the stations.
Also, it is desirable in the above described communications networks to use relatively long keys to encrypt and decrypt each message. This is because, in general, the degree of security which an encrypted message is given is proportional to the length of the key that is used to encrypt the message. However, long keys also require a large number of memory cells for their storage. For example, one million keys which are each one million bits long would require one billion storage cells, and that is impractical to achieve with today's technology.
Accordingly, a primary object of this invention is to provide a communication network which encrypts, transmits, and decrypts messages from one station to another without ever having to secretively transport encryption/decryption keys between the stations.
Another primary object of the invention is to provide a communication network in which messages are encrypted and decrypted with large numbers of long encryption/decryption keys without ever having to provide a large number of storage cells for those keys.